go.mod

@@ -24,6 +24,7 @@ require (
 	github.com/spf13/cobra v1.10.1
 	github.com/stretchr/testify v1.11.1
 	go.uber.org/fx v1.24.0
+	golang.org/x/sync v0.18.0
 	golang.org/x/term v0.37.0
 	gopkg.in/yaml.v3 v3.0.1
 	modernc.org/sqlite v1.38.0
@@ -266,7 +267,6 @@ require (
 	golang.org/x/exp v0.0.0-20251023183803-a4bb9ffd2546 // indirect
 	golang.org/x/net v0.47.0 // indirect
 	golang.org/x/oauth2 v0.33.0 // indirect
-	golang.org/x/sync v0.18.0 // indirect
 	golang.org/x/sys v0.38.0 // indirect
 	golang.org/x/text v0.31.0 // indirect
 	golang.org/x/time v0.14.0 // indirect

internal/vaultik/snapshot.go

@@ -8,6 +8,7 @@ import (
 	"regexp"
 	"sort"
 	"strings"
+	"sync"
 	"text/tabwriter"
 	"time"
 
@@ -16,6 +17,7 @@ import (
 	"git.eeqj.de/sneak/vaultik/internal/snapshot"
 	"git.eeqj.de/sneak/vaultik/internal/types"
 	"github.com/dustin/go-humanize"
+	"golang.org/x/sync/errgroup"
 )
 
 // SnapshotCreateOptions contains options for the snapshot create command
@@ -438,6 +440,9 @@ func (v *Vaultik) reconcileLocalWithRemote(remoteSnapshots map[string]bool) (map
 func (v *Vaultik) buildSnapshotInfoList(remoteSnapshots map[string]bool, localSnapshotMap map[string]*database.Snapshot) ([]SnapshotInfo, error) {
 	snapshots := make([]SnapshotInfo, 0, len(remoteSnapshots))
 
+	// remoteOnly collects snapshot IDs that need a manifest download.
+	var remoteOnly []string
+
 	for snapshotID := range remoteSnapshots {
 		if localSnap, exists := localSnapshotMap[snapshotID]; exists && localSnap.CompletedAt != nil {
 			totalSize, err := v.Repositories.Snapshots.GetSnapshotTotalCompressedSize(v.ctx, snapshotID)
@@ -458,16 +463,73 @@ func (v *Vaultik) buildSnapshotInfoList(remoteSnapshots map[string]bool, localSn
 				continue
 			}
 
-			totalSize, err := v.getManifestSize(snapshotID)
-			if err != nil {
-				return nil, fmt.Errorf("failed to get manifest size for %s: %w", snapshotID, err)
-			}
-
+			// Pre-add with zero size; will be filled by concurrent downloads.
 			snapshots = append(snapshots, SnapshotInfo{
 				ID:             types.SnapshotID(snapshotID),
 				Timestamp:      timestamp,
-				CompressedSize: totalSize,
+				CompressedSize: 0,
 			})
+			remoteOnly = append(remoteOnly, snapshotID)
+		}
+	}
+
+	// Download manifests concurrently for remote-only snapshots.
+	if len(remoteOnly) > 0 {
+		// maxConcurrentManifestDownloads bounds parallel manifest fetches to
+		// avoid overwhelming the S3 endpoint while still being much faster
+		// than serial downloads.
+		const maxConcurrentManifestDownloads = 10
+
+		type manifestResult struct {
+			snapshotID string
+			size       int64
+		}
+
+		var (
+			mu      sync.Mutex
+			results []manifestResult
+		)
+
+		g, gctx := errgroup.WithContext(v.ctx)
+		g.SetLimit(maxConcurrentManifestDownloads)
+
+		for _, sid := range remoteOnly {
+			g.Go(func() error {
+				manifestPath := fmt.Sprintf("metadata/%s/manifest.json.zst", sid)
+				reader, err := v.Storage.Get(gctx, manifestPath)
+				if err != nil {
+					return fmt.Errorf("downloading manifest for %s: %w", sid, err)
+				}
+				defer func() { _ = reader.Close() }()
+
+				manifest, err := snapshot.DecodeManifest(reader)
+				if err != nil {
+					return fmt.Errorf("decoding manifest for %s: %w", sid, err)
+				}
+
+				mu.Lock()
+				results = append(results, manifestResult{
+					snapshotID: sid,
+					size:       manifest.TotalCompressedSize,
+				})
+				mu.Unlock()
+				return nil
+			})
+		}
+
+		if err := g.Wait(); err != nil {
+			return nil, fmt.Errorf("fetching manifest sizes: %w", err)
+		}
+
+		// Build a lookup from results and patch the pre-added entries.
+		sizeMap := make(map[string]int64, len(results))
+		for _, r := range results {
+			sizeMap[r.snapshotID] = r.size
+		}
+		for i := range snapshots {
+			if sz, ok := sizeMap[string(snapshots[i].ID)]; ok {
+				snapshots[i].CompressedSize = sz
+			}
 		}
 	}
 
@@ -788,23 +850,6 @@ func (v *Vaultik) outputVerifyJSON(result *VerifyResult) error {
 
 // Helper methods that were previously on SnapshotApp
 
-func (v *Vaultik) getManifestSize(snapshotID string) (int64, error) {
-	manifestPath := fmt.Sprintf("metadata/%s/manifest.json.zst", snapshotID)
-
-	reader, err := v.Storage.Get(v.ctx, manifestPath)
-	if err != nil {
-		return 0, fmt.Errorf("downloading manifest: %w", err)
-	}
-	defer func() { _ = reader.Close() }()
-
-	manifest, err := snapshot.DecodeManifest(reader)
-	if err != nil {
-		return 0, fmt.Errorf("decoding manifest: %w", err)
-	}
-
-	return manifest.TotalCompressedSize, nil
-}
-
 func (v *Vaultik) downloadManifest(snapshotID string) (*snapshot.Manifest, error) {
 	manifestPath := fmt.Sprintf("metadata/%s/manifest.json.zst", snapshotID)